Java 银行程序帐户 ID 没有上升？

Question

每次创建银行账户时，账户 ID 都应该加一，但每次我尝试提取 ID 时，我得到的账户 ID 都是 0，任何建议，因为我完全按照书中的描述我正在学习，它仍然没有更新。

帐户构造器:

public class BankAccount {

    public static int bankID = 0;

    //constructor called by BankAccount michaelsBank = new BankAccount();
    public BankAccount(){
        balance = 0;
        lastAssignedNumber++;

        accountNumber = lastAssignedNumber;
    }

    //Constructs a bank account with an initial deposit, will be used if given a number for a parameter
    public BankAccount(double initialBalance){
        balance = initialBalance;
    }


        public void deposit(double amount){
            balance = balance + amount;
        }

        public void withdraw(double amount){
            balance = balance - amount;
        }

        public double getBalance(){
            return balance;
        }

        public int getID(){
            return accountNumber;
        }

        private double balance;
        private int accountNumber;
        private static int lastAssignedNumber;
}

银行账户主程序:

import java.text.*;

public class BankAccountTest {
 public static void main (String args[]){

            NumberFormat formatter = NumberFormat.getNumberInstance();
            formatter.setMaximumFractionDigits(2);  // Helps formatter format for final output
            formatter.setMinimumFractionDigits(2);
            ConsoleReader console = new ConsoleReader(System.in);

     System.out.println("Hello, would you like to make a new bank account?");
     String newA = console.readLine();

     if(newA.equalsIgnoreCase("yes")){
         System.out.println("How much would you like to deposit initially?");
         double init = console.readDouble();

         BankAccount account = new BankAccount(init);

         System.out.println("Your account is created, what would you like to do? \n 1: Get Balance \n 2: Get Account ID \n 3: Make a Withdrawl \n 4: Make a Deposit");
         int option = console.readInt();

         while(option == 1){
             System.out.println(account.getBalance() + " Is your balance. \nWhat would you like to do next?");
             System.out.println("1: Get Balance \n 2: Get Account ID \n 3: Make a Withdrawl \n 4: Make a Deposit");
             option = console.readInt();
         }
         while(option == 2){
             System.out.println(account.getID() + " Is your account id.\nWhat would you like to do next?");
             System.out.println("1: Get Balance \n 2: Get Account ID \n 3: Make a Withdrawl \n 4: Make a Deposit");
             option = console.readInt();
         }
         while(option == 3){
             System.out.println("How much would you like to withdraw?");
             double withdraw = console.readDouble();

             account.withdraw(withdraw);
             System.out.println("Your new balance is " + account.getBalance() + "\nWhat would you like to do next?");
             System.out.println("1: Get Balance \n 2: Get Account ID \n 3: Make a Withdrawl \n 4: Make a Deposit");
             option = console.readInt();
         }
         while(option == 4){
             System.out.println("How much would you like to deposit?");
             double deposit = console.readDouble();

             account.deposit(deposit);

             System.out.println("Your new balance is " + account.getBalance() + "\n what would you like to do next?");
             System.out.println("1: Get Balance \n 2: Get Account ID \n 3: Make a Withdrawl \n 4: Make a Deposit");
             option = console.readInt();
         }
     }

 }
}

Answer 1

您以一种杂乱无章的方式构建 BankAccount 对象，其中是否分配 ID 取决于您使用的构造函数。如果您重写您的构造函数，使它们链接在一起，一个主构造函数负责所有核心职责，一个辅助构造函数分配默认值并委托(delegate)给主构造函数，那么初始化将有一致的结果。

(术语是 Scala 的，构造函数链在该语言中是强制性的。)

这里的主要构造函数是:

public BankAccount(double initialBalance){
    balance = initialBalance;
    lastAssignedNumber++;
    accountNumber = lastAssignedNumber;
}

并添加一个辅助构造函数:

public BankAccount() {
    this(0);
}

无论您调用哪个，您都将获得一个生成的 ID。

(这类似于 Lorenzo's answer ，我赞成它清楚地描述了问题。不同之处在于他的链接是在另一个方向上进行的，因此默认值被分配然后被覆盖。)